counts 75 75 Photogaphic Alderneygannetries

The Northern Gannetries —

photographic counts of Ortac and

Les Etacs, in 2005

2 Jeremy+G. Sanders1 &Michael+P. Harris

Sanders J.G. & Harris M.P. 2005. The Alderney Northern Gannetries —

photographic counts of Ortac and Les Etacs, Channel Islands in 2005. Atlantic

Seabirds 7(2): 75-82. Aerial. surveys of Northern Gannet Morus bassanus colonies on

Ortac and Les Etacs, Channel Islands, in July 2005, found 2547 and 4862 Apparently

Sites The total increased 3.3% Occupied respectively. population at an average rate of per

annumover the last 55 years. There may now only be limited room for expansion on Ortac

increase in where the rate of has declined substantially recent years.

1 The Alderney Ornithological Group, P.O, Box 24, Alderney GY9 3AP, Channel

2 Islands; Centre for Ecology and Hydrology, Hill of Brathens, Banchory, AB31 4BW, Scotland, UK. E-mail; [email protected]

INTRODUCTION

The Channel Islands’ Northern Gannet Morus bassanus colonies are on the

of Ortac and Les Etacs, close to Alderney. In June 1940, the entire human population of Alderney, including a small military garrison, was evacuated to the UK. Prior to the evacuation, Major J.A.A. Wallace MC, who was

commanding the garrison, and some of his junior officers, visited Ortac to look

at a Black-legged Kittiwake Rissa tridactyla colony. One of his subalterns

reported in greatexcitement of “a big white bird like an albatross”. On climbing

to the top of the rock he discovered a Northern Gannet incubating an egg. Local

people assured him that it was the first (Lockley 1948), i.e., the first year the

species had bred. He also landed on Les Etacs several times, but there were no

Northern Gannets. The people of Alderney did not return until the war was

five hence the of and the initial over, years later, origin Les Etacs colony,

growth of the Ortac and Les Etacs colonies were not documented. However, in

1945 E. Quinain, an Alderney fisherman returning home after his enforced

absence, reported that the eastern side of Ortac was covered with Northern

Gannets and discovered another colony on Les Etacs, just off the western end of

Alderney (Dobson & Lockley 1946). Here, we report on counts derived from an

aerial survey undertaken in July 2005, and we also list previous counts. 76 J.G. Sanders &.M.P, Harris Atlantic Seabirds 7(2)

Les Etacs 1979 in (top) and 2005 (bottom). Les Etacs in 1979 (boven) en in 2005

(onder). (Mike Hill 1979& Jeremy Sanders 2005) counts 77 77 Photogaphic Alderneygannetries

METHODS

Both colonies were photographed between 1800 and 1900 hrs BST on 12 July

2005 using 100 ASA colour film and 35 mm cameras fitted with 28-90 mm lenses. Photographs were taken through the windows of a single-engine, high-

wing aircraft flying at about 200 m altitude. The weather was fine and the

in sunshine. Additional gannetries were photographs of Les Etacs were taken from the adjacent mainland of Alderney on 20 July 2005, and of Ortac and Les

from boat 6 2005. for made from the Etacs a on August Counts Ortac were aerial photographs but 17% of the final total for Les Etacs came from the later photographs.

Northern Gannets on Les Etacs are used to aircraft, since 20-50 small aircraft using Alderney’s airfield pass over daily, and non-breeding or ‘club’ birds did not take off when the aerial photographs were being taken. Fewer aircraft pass over Ortac and some, but not all, club birds took off. The August boat trip allowed the breeding areas to be delimited.

Three complete counts were made from 30x20 cm colour prints overlaid with sheet and third tracing paper (first count) or acetate (second counts). When counting, natural rock features were used as reference divisions to avoid double counting on different photographs. The count unit used was the Apparently

Occupied Site (AOS) defined as one or two Northern Gannets occupying a site,

of whether nest material visible. Counts made the irrespective any was were by senior author using a x8 magnifying glass, each AOS being spotted out as it was

counted.

Some previous counts have reported on the numbers of club-birds present. We did not do this since it was unclear how many had left due to the aircraft and because there birds the and the were many on sea on Renonquet reef, situated 1.5 km north-east of Ortac and 3.5 km north-west of Les Etacs.

started Northern Gannets roosting on Renonquet in 1999. The reef is low-lying, and there has so far been no evidence of Northern Gannets attempting to nest on

it.

RESULTS

Ortac Ortac is an isolated rock, approximately 100x70 m rising to 22 m in

situated west height, 4.5 km of Alderney; it has very steep sides. In 2005, there were 1865 AOS (range of three counts 1754-1944) on the east side and top, and

682 (567-784) on the west side, giving a total of 2547 (2321-2728) AOS.

Les Etacs The name Les Etacs is no longer in everyday use, although still used

and been the the Garden on maps documents, having replaced by name Rocks.

Les Etacs consist of two groups of rocks, rising steeply from the sea. The areas 78 J.G. Sanders &.M.P. Harris Atlantic Seabirds 7(2)

of and names of the various rocks are essentially those Hill (1993). The largest

unit, the Main Rock at the western end of the Main Group, is approximately 120

and rises from the of The m long x 70 m wide, steeply sea to a height 37 m.

north face of the Main Rock shelves at an angle sufficient to enable Northern

Gannets to nest on the greater part of it, and has the major part of the colony.

The south face of the Main Rock is sheer, and birds nest only on outcrops.

Adjacent to the northeastern end of the Main Rock are two rocks called here

North Rock 1 (closest to the Main Rock), and North Rock 2 (which lies to the

north of North Rock 1). All three units are joined at very low tide. The East

Stacks unit which is about third the Main and comprise a one as big as Group,

consist of two stacks, the highest of which is 32 m high.

In 2005, the Main Rock had 3479 AOS (range 3327-3660), North Rock I

had 423 AOS (including an estimate of 100 nests in hidden areas; range 417- 429), North Rock 2 had 266 AOS (254-277), and the East Stacks had 694 ASO

(646-739). This gives a total of4862 AOS (4644-5105).

Table 1. Counts ofNorthern Gannets on Ortac, 1940-2005.

Tabel 1. 1940-2005. Tellingen van Jan-van-genten op Ortac,

Year Count Range Source

1940 1 nest Dobson (1952)

1946 250 pairs Dobson (1952)

Fisher & 1948 >234 nests Vevers(1951)

1949 225 pairs 200-250 Fisher & Vevers (1951)

1950 570 pairs Fisher & Vevers (1951)

1951 225 pairs K. Le Cocq (in Hill 1989)

1952 450 pairs 400-500 K. Le Cocq (in Hill 1989)

1960 925 nests Cramp etal. (1974); Anonymous (1961)

1969 1000 AON 800-1200 Cramp etal. (1974) Operation Seafarer records

1979 1787 AOS 1719-1871 Hill (1989)

1984 2062 AOS 1964-2142 Hill (1989)

1987 2211 AOS 2138-2284 Hill (1989)

1989 2106 AOS 1967-2194 Hill (1989)

1994 2098 AOS M.G. Hill (pers. comm.)

1999 2500 AOS J. Hooper (in Wanless et al. 2005)

2005 2547 AOS 2321-2728 This study

Previous counts It was not until June 1938 that (two) Northern Gannets were

recorded the of rocks in flying past Casquets group summer (Dobson 1952).

The single nest with an egg on Ortac in 1940 was almost certainly the first

breeding attempt (Dobson 1952), at least in historic times. By the time of the

next checks, in 1946, there were c. 250 pairs on Ortac and c. 200 pairs at the Phologaphic counts Alderneygannetries 79 79

new colony on Les Etacs (Fisher & Vevers 1951). Details of counts known to us are given in Tables 1 and 2. Most of these counts are documented by Hill

(1989). The units used in these counts varied - nests, pairs, Apparently

Occupied Nests (AON) and Apparently Occupied Sites AOS - so for convenience we follow the normally accepted convention of assuming that these are all equivalent when comparing counts (Wanless et al. 2005). There is some

since this is uncertainty regarding the very high count from Les Etacs in 1969 approximately double the counts of 1960 and 1973. Long (1981) reported that numbers at both colonies showed “a steady increase until about 1960 when they reached about 1000 at both sites, since when the totals seem to have remained

of fairly constant”. Wanless (1987) assigned a count 1120 site-holding

individuals and 71 club birds in the Main Colony in 1969 to W.A. Burridge, and

Hill (1989) presented a map showing that the extent of the colony increased

little between 1960 and 1974. it that the relatively Therefore, appears likely for trends count of 2000 nests in 1969 is erroneous and plotting population (see

Figure 1) a figure of 1000 pairs is used (Wanless 1987).

Table 2. Counts ofNorthern Gannets on Les Etacs, 1940-2005. n.c. =not counted.

Tabel 2. Tellingen van Jan-van-gentenop Les Etacs, 1940-2005. n.c. = niet geteld.

Total Main East Year Source colony colony stack

1940 0 0 0 Dobson (1952)

Dobson 1946 200 nests 190 10 (1952)

1948 >200 nests Fisher & Vevers (1951)

1949 418 pairs 400 18 Fisher & Vevers (1951)

1950 615 pairs 600 15 Fisher & Vevers (1951)

Cramp et al. (1974); Unpublished 1960 1010 pairs 1000 10 Fisher British Museum J. papers, Anonymous (1961); Unpublished 1960 1062 nests 1000 62 J. Fisher papers, British Museum

1969 [2000 nests] Cramp et al. (1974)

Hill 1973 > 1003 AOS 1003 n.c (1989)

1974 1269 AOS 1019 c.50 Wanless (1987)

1975 1627 AOS 1525 102 Wanless (1987)

1979 1978 AOS 1891 87 Hill (1989)

1984 2325 AOS 2207 118 Hill (1989)

1987 2536 AOS 2412 124 Hill (1989)

1989 2810 AOS 2655 155 Hill (1989)

1992 2746 AOS 2535 211 M.G. Hill (pers. comm.)

1994 3380 AOS 3008 372 M.G. Hill (pers. comm.)

1999 3450 AOS J. Hooper (in Wanless etal. 2005)

2005 4862 AOS 4168 694 This study 80 J.G. Sanders &.M.P. Harris Atlantic Seabirds 7(2)

Figure 1 Number ofNorthern Gannet breeding sites (AON/AOS/nests/pairs) on Ortac

andLes Etacs, 1940-2005.

1. Figuur Aantal broedplaatsen (AON/AOS/nest/paar) van Jan-van-genten op Ortac en Les Etacs, 1940-2005.

DISCUSSION

There must have been massive immigration into these two colonies during and immediately after the war years to allow the increase from 1 to c. 450 nests over a five-year period and to 1185 nests by 1950. The increase has continued, albeit

of at a slightly reduced rate (Figure 1). Between 1950 and 2005, the rate increase of the two colonies combined has been remarkably constant at 3.3% per 2 = the of increase annum (9 counts, r 97%, P < 0.001). However, rate on Ortac between 1979 and 2005 was only 1.2% p.a., compared with 3.3% on Les Etacs.

The literature of seabird colonies that comprises many accounts appeared to have been full, but which have subsequently increased. Dobson & Lockley

(1946) speculated that the maximum capacities of Ortac and Les Etacs were 500 and perhaps 1000 pairs respectively. In 2005, there were about five times as

these the much reduced rate of increase many pairs as predictions. However, on

Ortac does suggest that space may be becoming limited. counts 81 81 Photogaphic Alderneygannetries

The Channel Island colonies were not counted during the British and

Irish Northern Gannet survey in 2003/04, and Wanless et al. (2005) assumed a figure of 6500 AOS based on the past rate of increase. This would now appear to have been slightly too low but even so, these two gannetries still hold less than 3% of the total British and Irish population (c. 260,000 occupied AOS;

Mitchell et al 2004). However, whereas the average rate of increase of the

British and Irish population since the last full survey had declined to 1.2% p.a., that in the Channel Islands had remained high at 2.8% p.a. The rate of increase

km from has also declined at the large French colony on Rouzic (135 Alderney) in recent years (Siorat & Bentz 2004) so it will be interesting to see what

numbers and in the future. happens to on Ortac Les Etacs near

ACKNOWLEDGEMENTS

We are indebted to Richard Herivel for pilotingthe aircraft for the aerial part ofthe census and Mike

Hill for encouragement and help.

Jan—van—gentenkoloniesop Alderney,

inventarisatievan Ortac en Les Etacs,

Kanaaleilanden,in 2005

Een inventarisatie vanuit de lucht kolonies Morus bassanus colonies Orlac van van Jan-van-gent op in in en Les Etacs (Kanaaleilanden) juli 2005, resulteerde respectievelijk 2547 en 4862 schijnbaar bezette plekken (Apparently Occupied Sites). De totale populatienam de afgelopen 55 jaar toe met

de een jaarlijks gemiddelde van 3.3% . Mogelijk is ruimtegebrek op Ortac nu beperkendefactor

toename. deze kolonie is de de laatste sterk voor een verdere In groeisnelheid jaren gedaald.

REFERENCES

Anonymous. 1961. Report and Transactions for the year 1960 of La Societe Guernesiaise. Vol.

XVII, Part 1, Ornithological Report, .

Cramp S., Bourne W.R.P. & Saunders D. 1974, The seabirds of Britain and Ireland, Collins,

London.

Dobson R. 1952. The birds of the Channel Islands. Staples Press, London.

Dobson R. & Lockley R.M. 1946. Gannets breeding in the Channel Islands. Brit. Birds. 39: 309-

321.

Fisher J. & Vevers H.G. 1951. The present population ofthe North Atlantic Gannet (Sula bassana). Proc, Int. Om. Congress 10:463-467.

Hill M.G. 1989. The Alderney gannetries - photographic counts of Ortac and Les Etacs, Channel

Islands, 1979-1989. Seabird 12:45-52.

Hill M.G. 1993. Seabirds ofthe . La Societe Guernesiaise, Guernsey. Lockley R.M. 1948. First breeding ofGannets in the Channel Islands, Brit. Birds 41: 216. Long R 1981. Review of birds in the Channel Islands, 1951-1980. British Birds 74: 327-344.

Mitchell P.I., Newton S., Ratcliffe N. & Dunn T. 2004. Seabird populations ofBritain and Ireland:

T. A.D. Results ofthe Seabird 2000 survey (1998-2002). & Poyser, London. 82 J.G. Sanders &.M.P. Harris Atlantic Seabirds 7(2)

Siorat F. & Bentz G. 2004. Reserve naturelle des Sept-Iles, Rapport d’activite 2004. Liguepourla

Prorection des Oiseaux, Rochefort.

Wattless S. 1987. A ofthe numbers and distribution of the North Atlantic Gannet survey breeding

and assessment of changes since 1969/70. Nature Conservancy Council, Peterborough.

Wanless S., Murray S. & Harris M.P. 2005. The status of the Northern Gannet in Britain & Ireland

in 2003/04. Brit. Birds 98; 280-294.